Expression of K+ channels in normal and cancerous human breast

Potassium (K+) channels contribute to the regulation of cell proliferation and apoptosis and are also involved in tumor generation and malignant growth. Using immunohistochemical analysis, we investigated the expression of four K+ channels GIRK1 (G-Protein Inwardly Rectifying Potassium Channel 1), Ca2+-activated K channel (KCa1.1), voltage activated K+ channels (KV 1.1 and KV 1.3) and of the anti-apoptotic protein Bcl2 in normal and cancerous breast tissues and compared their expression with clinicopathological data. GIRK1 was overexpressed in carcinomatous tissues. In contrast, KV 1.1 and KV 1.3 were less expressed in cancerous tissue. The expression of Bcl-2 was similar in both tissues. As to the clinicopathological data, a correlation between KCa1.1 channel and estrogen receptor (ER) expression was observed. GIRK1 was overexpressed in breast carcinoma suggesting its involvement in proliferation and oncogenesis and its possible use as a putative pharmaceutigal target. The correlation between KCa1.1 channel and ER suggests the involvement of this channel in proliferation. The loss of expression of the two channels KV 1.1 and KV 1.3 may correspond to their role in apoptosis.